QwtPlotDirectPainter(3)        Qwt User's Guide        QwtPlotDirectPainter(3)

NAME
       QwtPlotDirectPainter - Painter object trying to paint incrementally.


SYNOPSIS
       #include <qwt_plot_directpainter.h>

       Inherits QObject.

   Public Types
       enum Attribute { AtomicPainter = 0x01, FullRepaint = 0x02,
           CopyBackingStore = 0x04 }
           Paint attributes.
       typedef QFlags< Attribute > Attributes

   Public Member Functions
       QwtPlotDirectPainter (QObject *parent=NULL)
           Constructor.
       virtual ~QwtPlotDirectPainter ()
           Destructor.
       void setAttribute (Attribute, bool on)
       bool testAttribute (Attribute) const
       void setClipping (bool)
       bool hasClipping () const
       void setClipRegion (const QRegion &)
           Assign a clip region and enable clipping.
       QRegion clipRegion () const
       void drawSeries (QwtPlotSeriesItem *, int from, int to)
           Draw a set of points of a seriesItem.
       void reset ()
           Close the internal QPainter.
       virtual bool eventFilter (QObject *, QEvent *) override
           Event filter.

Detailed Description
       Painter object trying to paint incrementally.

       Often applications want to display samples while they are collected.
       When there are too many samples complete replots will be expensive to
       be processed in a collection cycle.

       QwtPlotDirectPainter offers an API to paint subsets ( f.e all additions
       points ) without erasing/repainting the plot canvas.

       On certain environments it might be important to calculate a proper
       clip region before painting. F.e. for Qt Embedded only the clipped part
       of the backing store will be copied to a ( maybe unaccelerated ) frame
       buffer.

       Warning
           Incremental painting will only help when no replot is triggered by
           another operation ( like changing scales ) and nothing needs to be
           erased.

       Definition at line 39 of file qwt_plot_directpainter.h.

Member Typedef Documentation
   typedef QFlags<Attribute > QwtPlotDirectPainter::Attributes
       An ORed combination of Attribute values.

       Definition at line 73 of file qwt_plot_directpainter.h.

Member Enumeration Documentation
   enum QwtPlotDirectPainter::Attribute
       Paint attributes.

       See also
           setAttribute(), testAttribute(), drawSeries()

       Enumerator

       AtomicPainter
              Initializing a QPainter is an expensive operation. When
              AtomicPainter is set each call of drawSeries() opens/closes a
              temporary QPainter. Otherwise QwtPlotDirectPainter tries to use
              the same QPainter as long as possible.

       FullRepaint
              When FullRepaint is set the plot canvas is explicitly repainted
              after the samples have been rendered.

       CopyBackingStore
              When QwtPlotCanvas::BackingStore is enabled the painter has to
              paint to the backing store and the widget. In certain
              situations/environments it might be faster to paint to the
              backing store only and then copy the backing store to the
              canvas. This flag can also be useful for settings, where Qt
              fills the the clip region with the widget background.

       Definition at line 46 of file qwt_plot_directpainter.h.

Member Function Documentation
   QRegion QwtPlotDirectPainter::clipRegion () const
       Returns
           Currently set clip region.

       See also
           setClipRegion(), setClipping(), hasClipping()

       Definition at line 151 of file qwt_plot_directpainter.cpp.

   void QwtPlotDirectPainter::drawSeries (QwtPlotSeriesItem * seriesItem, int
       from, int to)
       Draw a set of points of a seriesItem. When observing an measurement
       while it is running, new points have to be added to an existing
       seriesItem. drawSeries() can be used to display them avoiding a
       complete redraw of the canvas.

       Setting plot()->canvas()->setAttribute(Qt::WA_PaintOutsidePaintEvent,
       true); will result in faster painting, if the paint engine of the
       canvas widget supports this feature.

       Parameters
           seriesItem Item to be painted
           from Index of the first point to be painted
           to Index of the last point to be painted. If to < 0 the series will
           be painted to its last point.

       Definition at line 172 of file qwt_plot_directpainter.cpp.

   bool QwtPlotDirectPainter::hasClipping () const
       Returns
           true, when clipping is enabled

       See also
           setClipping(), clipRegion(), setClipRegion()

       Definition at line 125 of file qwt_plot_directpainter.cpp.

   void QwtPlotDirectPainter::setAttribute (Attribute attribute, bool on)
       Change an attribute

       Parameters
           attribute Attribute to change
           on On/Off

       See also
           Attribute, testAttribute()

       Definition at line 86 of file qwt_plot_directpainter.cpp.

   void QwtPlotDirectPainter::setClipping (bool enable)
       En/Disables clipping

       Parameters
           enable Enables clipping is true, disable it otherwise

       See also
           hasClipping(), clipRegion(), setClipRegion()

       Definition at line 116 of file qwt_plot_directpainter.cpp.

   void QwtPlotDirectPainter::setClipRegion (const QRegion & region)
       Assign a clip region and enable clipping. Depending on the environment
       setting a proper clip region might improve the performance heavily.
       F.e. on Qt embedded only the clipped part of the backing store will be
       copied to a ( maybe unaccelerated ) frame buffer device.

       Parameters
           region Clip region

       See also
           clipRegion(), hasClipping(), setClipping()

       Definition at line 141 of file qwt_plot_directpainter.cpp.

   bool QwtPlotDirectPainter::testAttribute (Attribute attribute) const
       Returns
           True, when attribute is enabled

       Parameters
           attribute Attribute to be tested

       See also
           Attribute, setAttribute()

       Definition at line 105 of file qwt_plot_directpainter.cpp.


Author
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Version 6.2.0                   Sun Jul 18 2021        QwtPlotDirectPainter(3)